first=float(input('请输入一个数:'))
second=float(input('请输入第二个数:'))
operator=input('请选择运算符:+ - * /:')
if operator =='+':
    print(first+second)
elif operator =='-':
    print(first-second)
elif operator=='*':
    print(first*second)
elif operator=='/':
    print(first/second)